“Waterfall R. C. et al.: Visualizing combustion using electrical impedance tomography, Chemical Engineering Science, Vol. 52, No. 13, pp. 2129-2138, 1997” discloses the monitoring of the combustion process in an internal combustion engine, wherein the complex impedance of the plasma obtained in the combustion chamber during the ignition is measured and evaluated. When determining the complex impedance a wide frequency range can also be used in the process. The techniques developed for an electrical capacity tomography were adapted in a scaled model of an engine with internal combustion for characterizing combustion phenomena. The method can locate the flame position, measure the flame size and monitor the effect of a changed air/fuel ratio. Combustion misfires can be identified. The technique can measure the arrival time of the flame front and reliably present the development of the combustion process in a research model of a one-cylinder engine with internal combustion.
DE 697 13 226 T2 discloses a diagnostic method for the ignition of an internal combustion engine by registering the ionizing signal of the gases in the cylinders of the engine having an ignition coil, whose primary winding is connected with an electronic power module for the ignition, and whose secondary winding is connected with at least one plug of a cylinder. The diagnostic method comprises a first leg for the frequency compensation of the coil in order to increase its resonant frequency to a value which is twice the size of the frequency of the ionizing signal to be registered. The diagnostic method additionally comprises a second leg for measuring the ionizing impedance of the gases with activation of the primary control of the coil through a constant amplitude current which is supplied by a vibration pickup controlled by the parallel resonant frequency of the coil and activating the voltage at the terminals of the coil.
DE 10 2004 039 406 A1 discloses a plasma ignition method and device for igniting fuel/air mixtures in internal combustion engines. To ignite fuel/air mixtures in at least one combustion chamber of an Otto cycle engine the following steps are carried out: ignition of an HF gas discharge as main discharge for generating a plasma channel in the region of the boundary between an ignition element and the combustion chamber; preceding or maximally simultaneous ignition of an HF gas discharge as auxiliary discharge for generating a flow directed at the plasma channel, wherein the auxiliary discharge is positioned behind the main discharge from the combustion chamber, so that the directed flow presses the plasma channel of the main discharge into the combustion chamber.
The research report “BNDF: Plasma technology, Research Report May 2000, Page 16” discloses a new type of plasma ignition. The principle of the plasma ignition introduced here however utilizes an ignition mechanism in the nano-second range. This brings with it several advantages: the electrode arrangement can be configured so that no parts protrude into the combustion chamber any longer. A plasma beam securely reaches the layers of ignitable mixtures in the sophisticated combustion zones especially in modern gasoline direct injection engines.
In the case of drives for internal combustion engines the requirements in terms of power and pollutant emission are increasingly raised. In the case of modern drives for gasoline engines, engines are therefore being developed in which a gasoline-air mixture is ignited in the combustion chamber of the individual cylinders with a high-frequency plasma. Such an ignition system for internal combustion engines is known for example from DE 31 29 954 C2.
In order to minimize the number of ignition misfires the plasma combustion duration as well as the plasma capacity is selected so large that the plasma energy is adequate in all cases to safely ignite the gasoline-air mixture. Thus, however, these quantities are identical for all cylinders and often selected too large. However, this is accompanied by a high load of the electrodes at the tip of the resonator. In addition, the system often absorbs unnecessary energy since the additional plasma effect provided for safety reasons does not provide any advantages after a completed ignition.
To monitor the combustion process only signals of additionally provided sensors can be used with the currently employed high-frequency systems, which however would have to be additionally integrated in the vehicle. In addition to this, these sensors do not work cylinder-specifically but transmit results which allow conclusions only for the entire combustion process of the internal combustion engine.